CTSD and Huntington disease: The lysosomal pathology in affected neurons in late-stage HD brains (Figs. 4, 5) involved the accumulation of CTSD positive vesicles, which were decorated by HTT (Fig. 5B–D) and concentrating in one pole of the neuron (Figs. 4C, E and 5D), a distribution pattern associated with lipofuscin granules.